1. Field of the Invention
The present invention relates to a vibration generating device adapted to be built in a game controller or the like for vibrating the controller itself or for alerting signal reception in a portable cellular telephone or a pager unit, and a method for mounting a weight to the vibration generating device.
2. Description of Related Art
FIG. 8 is a front view for explaining a method of mounting a weight to a motor shaft in a conventional vibration generating device, showing the state of the weight before mounting. FIG. 9 is a front view showing the state of the weight after mounting.
The conventional weight 10 stated above has a body 11 of a semicircular columnar section, and is provided with a U-groove 4 formed at the center in the diametral direction of the body 11, for the insertion of a motor shaft 3. On both sides of the U-groove 4 projections 13a and 13b are formed upwardly.
When the aforesaid weight 10 is mounted on the shaft 3, the shaft 3 is inserted first into the U-groove 4 of the weight 10 and supported in position. Next, a support block 1 is used to support the weight 10 thereon. The supporting surface of the support block 1 has the same configuration as the perimeter (curved portion) of the weight 10, so that the perimeter of the weight 10 will be fitted in the curved portion 1a of the support block 1, with the flat portion of the weight 10 held level.
Subsequently a pressing member 12 with a recess portion 12a of a triangular section is lowered from above the weight 10 until the weight 10 is fastened on the shaft 3. That is, the surface area of the recess portion 12a formed in the forward end of the pressing member 12 is formed smaller than the surface area formed by the projections 13a and 13b and by a space between the projections 13a and 13b. Therefore the recess portion 12a of the pressing member 12 is fed downwardly into contact with the tips of the projections 13a and 13b and is further pressed downwardly to bend both projections 13a and 13b inwardly (in the directions of the arrows R and L), thereby caulking the weight 10 to the shaft 3.
However, the conventional weight 10 and the method of mounting the same as shown in FIGS. 8 and 9 have the problem that the vibration generating device is suitable for use where the weight 10 is produced of a relatively soft material such as copper. In the case of the weight 10 produced of a relatively hard material such as iron, a great load is required when the weight 10 is mounted to the shaft 3.
If a small load is applied when mounting the weight 10 to the shaft 3, the weight 10 mounted by a conventional method can easily be removed from the shaft 3 with a relatively little force; it is likely, therefore, that when a motor using the weight 10 is in practical use, the weight 10 will move out of position on the shaft 3 during rotation (during use), producing a noise or coming off from the shaft to impair the device itself.
In the weight 10 having the U-groove 4 shown in FIGS. 8 and 9, the inside wall surface of the U-groove 4 is formed straight, and therefore it is necessary to largely deform the straight inside wall surface into a curved surface along the perimeter of the shaft 3 by applying a pressure by the pressing member 12, that is, by applying a great load to the projections 13a and 13b. Therefore the projections 13a and 13b, if applied with a little load, will be insufficiently deformed, resulting in a small contact surface area between the inside wall surface of the U-groove 4 and the curved surface of the shaft 3. Consequently the mounting pressure will decrease and the weight 10 will come off the shaft 3 if a weight mounted is a large type and accordingly an increased load is applied to the weight.